import sys
import pygame
from bullet import Bullet
from alien import Alien
from time import sleep

def check_keydown_events(event,ai_settings, screen, ship, bullets):     #若检测到键盘活动
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()

def fire_bullet(ai_settings, screen, ship, bullets):
    """如果还没有到达限制就发射子弹"""
    if len(bullets) < ai_settings.bullet_allowed:
            new_bullet = Bullet(ai_settings, screen, ship)
            bullets.add(new_bullet)

def check_keyup_events(event, ship):
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens,
    bullets):                         #检查是否退出
    for event in pygame.event.get():                   #检测键盘鼠标事件
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, ai_settings, screen, ship , bullets)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(ai_settings, screen, stats, sb, play_button,
                ship, aliens, bullets, mouse_x, mouse_y)

def check_play_button(ai_settings, screen, stats, sb, play_button,
        ship, aliens, bullets, mouse_x, mouse_y):
    """在玩家单击Play按钮时开始游戏"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:

        #重置游戏设置
        ai_settings.initialize_dynamic_settings()

        #隐藏光标
        pygame.mouse.set_visible(False)
        if play_button.rect.collidepoint(mouse_x, mouse_y):
            #重置游戏统计信息
            stats.reset_stats()
            stats.game_active = True

            #重置记分牌图像
            sb.prep_score()
            sb.prep_high_score()
            sb.prep_level()
            sb.prep_ships()

            #清空外星人列表和子弹列表
            aliens.empty()
            bullets.empty()

            #创建一群新的外星人，并让飞船居中
            create_fleet(ai_settings, screen, ship, aliens)
            ship.center_ship()

def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets,
        play_botton):
    screen.fill(ai_settings.bg_color)                        #设置背景颜色 
    for bullet in bullets.sprites():
        bullet.draw_bullet()                    
    ship.blitme()                                              #显示飞船
    aliens.draw(screen) 

    #显示得分
    sb.show_score()

    #如果游戏处于非活动状态，就绘制play按钮
    if not stats.game_active:
        play_botton.draw_button()

    #让最近绘制的屏幕可见
    pygame.display.flip()                                    #让最近绘制的屏幕可见

    
def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """更新子弹位置，并删除已经消失的子弹"""
    bullets.update()
    #删除已经消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)
    check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
            aliens, bullets)
    

def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
         aliens, bullets):
    #检查是否有子弹击中外星人
    #如果是这样，就删除相应的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    """这个方法将每个子弹的rect和每个外星人的rect进行比较，并返回一个字典
    以子弹为键，被击中的外星人为键值"""
    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)
            sb.prep_score()
        check_high_score(stats, sb)
    if len(aliens) == 0:
        #删除现有的子弹并新建一外星人,并加快节奏
        bullets.empty()
        ai_settings.increase_speed()

        #提高等级
        stats.level += 1
        sb.prep_level()

        create_fleet(ai_settings, screen, ship, aliens)

def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)

    #创建外星人群
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)


def get_number_aliens_x(ai_settings, alien_width):
    #计算每行可容纳多少个外星人
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x

def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    #创建一个外星人并将其加入当前行
    alien = Alien(ai_settings, screen)  
    alien_width = alien.rect.width 
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)

def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height-
                            (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height))
    return number_rows

def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """检查是否有外星人位于屏幕边缘，更新外星人群中所有外星人的位置"""
    check_fleet_edges(ai_settings, aliens)
    aliens.update()

    #检测外星人和飞船之前的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        #spritecllideany接受两个实参。一个精灵一个编组，返回第一个碰撞的
        ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)

    check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets)

def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采用相应的措施"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break

def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移，并改变他们的方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1

def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """响应被外星人撞到的飞船"""
    if stats.ships_left > 0:
        #将ships_left-1
        stats.ships_left -= 1

        #更新记分牌
        sb.prep_ships()

        #清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        #创建一群新的外星人，并将飞船放到屏幕底端中央
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

        #暂停
        sleep(0.5)
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)

def check_aliens_bottom(ai_settings, screen , stats, sb, ship, aliens, bullets):
    """检查是否有外星人到达了屏幕低端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            #和处理飞船一样
            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
            break

def check_high_score(stats, sb):
    """检查是否诞生了新的最高得分"""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score()